一段代码阐述一个轮播思路

摘要：一段代码阐述一个轮播思路不，直接上代码如果是下一个，那就先吧下个的设置成来移动位置，防止用户看到将下个放到指定的位置开始轮播注意以上只是主思路代码，完整的代码解读完之后会贴出来供大家参考。

1. if (direction === "next") {
2.     this.index = nextIndex;
3.     /*如果是下一个，那就先吧下个的dom设置成none来移动位置，防止用户看到*/
4.     nextEl.style.display = "none";
5.     nextEl.style.webkitTransition = "";
6.     currentEl.style.display = "block";
7.     currentEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
8.     setTimeout(()=> {
9.         /*将下个放到指定的位置*/
10.         nextEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
11.         nextEl.style.display = "block";
12.         nextEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
13.         setTimeout(() => {
14.             /*开始轮播*/
15.             currentEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
16.             nextEl.style.webkitTransform = `translate3d(0, 0, 0)`;
17.         }, 20);
18.     }, 10);
19. } 

注意：以上只是主思路代码，完整的代码解读完之后会贴出来供大家参考。

代码解读：思路是先判断滚动方向，如果是向下一个节点那我就准备下一个节点到指定位置（仅适合界面一次展示一个轮播节点），如果直接移动到指定位置肯定是不合理的，因为节点直接移动会让用户在浏览器界面看到，可是节点是肯定要移动啊，思路很简单，那我给节点穿一件隐身衣（display:none）,之后再移动到指定位置用户不就看不到了，但是注意这里存在一个问题，如果直接设置设置display：none之后立马就移动位置的话会存在一个问题，移动的效果用户仍然能看的到，这是因为非异步的JS代码在执行的过程中是会阻止浏览器的绘图和重绘的，所以为了绕开浏览器这个机制那就使用异步好了（setTimeout）,下一个节点的位置现在已经准备好了，现在如果还是直接移动的话，又会存在一个问题下一个节点竟然看不到移动，这是因为我们在准备节点的节点的时候已经将它隐藏了，所以为了让用户看到就不得不把隐身衣脱了（display:block）才行，这样又得加一个异步（setTimeout）才能生效了，现在就可以安心的执行当前节点和早已就绪的下一个节点了。

下面的轮播JS部分的代码是vue写的，主要功能包括了垂直轮播，水平轮播，手势轮播等几个轮播的主要功能

export default {
    name: "swipe",
    props: {
        /*默认是水平滚动*/
        toward: {
            type: String,
            default: "vertical"
        },
        /*是否展示指示标志*/
        showIndicators: {
            type: Boolean,
            default: true
        },
        /*滚动速度*/
        speed: {
            type: Number,
            default: 300
        },
        /*默认下标从哪儿开始*/
        defaultIndex: {
            type: Number,
            default: 0
        },
        /*自动滚动间隔*/
        interval: {
            type: Number,
            default: 3000
        }
    },
    data() {
        return {
            dots: [],    // 页面标记圆点
            index: this.defaultIndex,   //当前页面的下标
            pageEls: [],   // 所有的子轮播项集合
            timer: null, //轮播定时器对象
            noSwipe: false,  //禁止滚动
            startPosition: "",  //touch的起始位置
            currentPosition: "",  //touch的目前位置
            translatePosition: "",  //touch位移的位置
            distance: 10,    //touch的位移大于10的时候生效
        }
    },
    watch: {},
    beforeMount: function () {
    },
    mounted(){
        this.initSwipe();
        this.swipeTimeout();
        this.initTouchEvent();
    },
    computed: {
        getNum(){
            return this.pageEls.length;
        },
    },
    methods: {
        /*手动上一张*/
        prev(){
            window.clearTimeout(this.timer);
            this.swipeTimeout("prev");
        },
        /*手动下一张*/
        next(){
            window.clearTimeout(this.timer);
            this.swipeTimeout("next");
        },
        initTouchEvent(){
            let dom = this.$el.querySelector(".swipe-warp");
            dom.addEventListener("touchstart", this.handleTouchStart);
            dom.addEventListener("touchmove", this.handleTouchMove);
            dom.addEventListener("touchend", this.handleTouchEnd);
            console.log(dom);
        },
        /*初始化轮播节点*/
        initSwipe(){
            var children = this.$children;
            if (children.length === 1) {
                this.noSwipe = false;
                return;
            }
            children.forEach((child, _index)=> {
                this.pageEls.push(child.$el);
            });
        },
        /*定时轮播*/
        swipeTimeout(toward = "next"){
            this.translate(toward, ()=> {
                this.timer = window.setTimeout(()=> {
                    this.swipeTimeout("next");
                }, this.interval);
            });
        },
        /*滚动方法*/
        translate(direction = "next", cb){
            let length = this.pageEls.length;
            let currentIndex = this.index;
            let currentEl = this.pageEls[currentIndex];
            let nextIndex = ((this.index + 1) > (length - 1)) ? 0 : (this.index + 1);
            let nextEl = this.pageEls[nextIndex];
            let pervIndex = (this.index - 1) < 0 ? (length - 1) : (this.index - 1);
            let pervEl = this.pageEls[pervIndex];
            if (direction === "next") {
                this.index = nextIndex;
                /*如果是下一个，那就先吧下个的dom设置成none来移动位置，防止用户看到*/
                nextEl.style.display = "none";
                nextEl.style.webkitTransition = "";
                currentEl.style.display = "block";
                currentEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
                setTimeout(()=> {
                    /*将下个放到指定的位置*/
                    nextEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
                    nextEl.style.display = "block";
                    nextEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
                    setTimeout(() => {
                        /*开始轮播*/
                        currentEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
                        nextEl.style.webkitTransform = `translate3d(0, 0, 0)`;
                    }, 20);
                }, 10);
            } else {
                this.index = pervIndex;
                /*如果是上一个，那就先吧上个的dom设置成none来移动位置，防止用户看到*/
                pervEl.style.display = "none";
                pervEl.style.webkitTransition = "";
                currentEl.style.display = "block";
                currentEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
                setTimeout(()=> {
                    /*将上个放到指定的位置*/
                    pervEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(-100%, 0, 0)` : `translate3d(0, -100%, 0)`;
                    pervEl.style.display = "block";
                    pervEl.style.webkitTransition = "-webkit-transform " + this.speed + "ms ease-in-out";
                    setTimeout(() => {
                        /*开始轮播*/
                        currentEl.style.webkitTransform = this.toward === "horizontal" ? `translate3d(100%, 0, 0)` : `translate3d(0, 100%, 0)`;
                        pervEl.style.webkitTransform = `translate3d(0, 0, 0)`;
                    }, 20);
                }, 10);
            }
            this.once(currentEl, "webkitTransitionEnd", ()=> {
                cb && cb();
            });
        },
        handleTouchStart($evnet){
            this.startPosition = this.toward === "horizontal" ? $evnet.touches[0].clientX : $evnet.touches[0].clientY;
        },
        handleTouchMove($evnet){
            this.currentPosition = this.toward === "horizontal" ? $evnet.touches[0].clientX : $evnet.touches[0].clientY;
            this.translatePosition = this.currentPosition - this.startPosition;
            this.translatePosition !== 0 && window.clearTimeout(this.timer);
            $evnet.preventDefault();
            $evnet.stopPropagation();
        },
        handleTouchEnd($evnet){
            this.translatePosition < 0 && this.translatePosition < -this.distance && this.swipeTimeout("next");
            this.translatePosition > 0 && this.translatePosition > this.distance && this.swipeTimeout("prev");
        },
        /*管理事件*/
        once(el, event, fn) {
            var that = this;
            var listener = function () {
                if (fn) {
                    fn.apply(this, arguments);
                }
                that.off(el, event, listener);
            };
            this.on(el, event, listener);
        },
        /*监听事件*/
        on(element, event, handler){
            if (element && event && handler) {
                element.addEventListener(event, handler, false);
            }
        },
        /*移除事件*/
        off(element, event, handler) {
            if (element && event) {
                element.removeEventListener(event, handler, false);
            }
        }
    }
};